Construction and Operation of Experimental Simulator with

Thermodynamic Modeling

John Koch (NSF SURF Mentee)Manpreet Bham

Dr. David K. Jeong (NSF SURF Mentor)

Mechanical Engineering, Arkansas State University

John Koch

Content

• Background

• Research Objectives

• Construction and Operation

• Thermodynamic Modeling

• Results and Discussions

• Conclusion

• Future Work

• Acknowledgements

John Koch

Background: CSP

Thermal Energy Storage with

Molten Salts

HotCold

Parabolic Trough

Technology

SOURCE: http://johnbrianshannon.com/spain/Manpreet Bham

Background: CSP• Typical thermal efficiency of renewable power plant is about 10%

• Energy is stored though the phase transition from solid to liquid form of the molten salts

• Energy is released through the phase transition from liquid to solid form during recrystallization of molten salts

• The recrystallization of the molten salts is used to create steam through heat transfer to power a steam turbine

Q=mCpΔTm= mass of molten salt

Cp= Specific Heat of Salt

ΔT= Temperature change

Manpreet Bham

Background: Molten Salts

• Liquid phase of salts that are solids at ambient temperature

• Typical synthetic salt temperature range (NaNO3-KNO3): 220-550°C

• Applications

– Heat transfer fluids for thermal energy storage in Concentrated Solar Power Plants (CSP) or other industrial applications

– Primary and secondary moderators for Nuclear Molten Salt Reactor

• Problem: Keeping the salts in molten phase

Manpreet Bham

Research Objectives

– Use computational methods to find the eutectic temperature and melting point of molten salt alternatives• Using Total Gibbs Energy Minimization

– G = H - TS

– Compare the computational results with experimental data

– Develop more efficient synthesized molten salt for CSP (Mixture of three nitrates: NaNO3,LiNO3,KNO3)

– Validate results with experimental simulator for long term operation

John Koch

Experimental Simulator

• Small scale simulator to test the performance of molten salt developed in our laboratory

• Simulator design mainly focused on molten salt region of Andasol Plant– Using Reynolds's, Thermal

and Geometric analogy of Andasol Plant (6000:1)

• First simulator in the world– 3 other universities have also

targeted construction similar simulators

John Koch

Experimental Simulator• Thermal energy storage simulator

• Equipment:

– 5.5 gallon tank with heating ring

– 0.5 hp Pump Motor

– Closed Pipe loop with heating coil

– K Type Thermocouples

– Watlow EZ-ZONE Controller

– Omega Multi-zone Controller

– 2 types of insulation held by TAPE

• Designed to produce results in time spans of 3, 6 and 9 months

• Maximum operating temperature for components is 500°C

John Koch

Experimental Simulator: Construction

• funded by ASTA and NSF– Design and construction of control panel

– Corrected spacing and orientation of the heating tapes around the pipes• Level the tanks and pipes

– Fabricate bridge for wires to run to the control panel

– Install bridge and connect the heating tapes, heating band, and thermocouples to the control panel

– Added Kaowool insulation around the piping over the heating tapes • After testing heated tapes and pump for appropriate behavior using water at 50°C as the

working fluid

– 20 days of observing the setup up running water at 50°C for leakage test

– Insulate tank with Kaowool insulation

John Koch

Experimental Simulator: Operation

• The system will be turned on

• The computer program will be started and calibrated

• Tank Containing Salts will be heated using Watlowcontroller

• Using Multi-Zone controller heating tapes on pipe will start transferring heat to maintain temperature

• Then pump on tank will be started to circulate the fluid at adjusted speed

• Temperature measurement program will start taking readings periodically

Manpreet Bham

Thermodynamic Modeling with Total Gibbs Energy Minimization

John Koch

Computational

• Program: Matlab R2011a

• NaNO3-KNO3 (Manpreet Bham)

• LiNO3-KNO3 (John Koch)

• Derivation of Gibbs Energy Minimization for a Binary System

• Develop programs for thermodynamic modeling to find melting point of binary salts

John Koch

Thermodynamic Modeling for Binary System (1/3)

EXCESSSTD

i

iitot GGGXG

2

1

ixsiiidi GXRTGG ,, )ln(

TT

T

TTC

T

TTHG mp

mp

p

mp

mp

fiid ln)(

,

2

21,

121,2,

1

21,

221,1,

X

GXGG

X

GXGG

xs

xsxs

xs

xsxs

Manpreet Bham

)ln(2121 cTTbTaXXG

1

21,

221,1,X

GXGG

xs

xsxs

2

21,

121,2,X

GXGG

xs

xsxs

Thermodynamic Modeling for Binary System (2/3)

LiNO3-KNO3 NaNO3-KNO3GIBBS EXCESS TERMS

)( 2112121 XcXbXaXXG

1

21,

221,1,X

GXGG

xs

xsxs

2

21,

121,2,X

GXGG

xs

xsxs

Manpreet Bham

2211 GXGXGtot

))ln(())ln(( 2,22,21,11,1 xsidxsid GXRTGXGXRTGX

)ln()1ln(ln)(

)1(

)ln()1()ln(ln)(

2

1122,

2,

2,

2,

2,

2,1

2

1111,

1,

1,

1,

1,

1,1

cTTbTaXXTRTTT

TTC

T

TTHX

cTTbTaXXTRTTT

TTC

T

TTHX

mp

mp

p

mp

mp

f

mp

mp

p

mp

mp

f

),( 1 TXfGtot

Thermodynamic Modeling for Binary System (3/3)

LiNO3-KNO3

2211 GXGXGtot

))ln(())ln(( 2,22,21,11,1 xsidxsid GXRTGXGXRTGX

)()1ln(ln)(

)1(

)2)(1()ln(ln)(

11122,

2,

2,

2,

2,

2,1

2

111111,

1,

1,

1,

1,

1,1

bXaXXTRTTT

TTC

T

TTHX

bXbXaXXTRTTT

TTC

T

TTHX

mp

mp

p

mp

mp

f

mp

mp

p

mp

mp

f

NaNO3-KNO3

Results: LiNO3-KNO3

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1350

400

450

500

550

600

650

mol KNO3

Te

mp

era

ture

(K

)

Figure 1. KNO3-LiNO3

w/o excess

Kleppa

ASU

• ASU data is from experimental method of DSC• Without excess is only the Standard Gibbs energy ( )

STDG

John Koch

Results: NaNO3-KNO3

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1400

450

500

550

600

650

Mol Fraction

Tem

pera

ture

[K

]

Figure. KNO3-NaNO3

w/o excess

Kleppa

ASU

KNO3Manpreet Bham

Conclusion

• Derived the Total Gibbs Energy Equation for binary system

• Mathematically modeled the Total Gibbs Energy minimization for predicting melting temperature or chemical composition at equilibrium

• Modeling accuracy can be enhanced by applying more accurate curve fitting regression method

• Accomplished construction of experimental simulator scaled down from Andasol CSP in Spain

John Koch

Future Work

• More accurate relationship for excess Gibbs energy in binary system– Experiment to find the coefficients

• Design computational modeling for ternary compounds– Compare with experimental data from the Differential

Scanning Calorimeter (DSC), Thermogravimetric Analyzer (TGA)

• Evaluate performance of salt with experimental simulator for long term application

John Koch

Ackowledgements

• Arkansas Science and Technology Authority (ASTA)

• National Science Foundation (NSF)

• Arkansas State University Office of Research & Technology Transfer (ORTT)

John Koch

THANK YOU!!